Hand aspirating psychrometer



May 23, 1939- R. R. CHAPPELI. Er Al. 2,159,133

HAND ASPIRATING PS YCHROMETER Filed June 26, 1936 INVENTOR. aal ha. cha lz 1:11314 scezneth .wgfng,

BY /f/@m m Patented May 23, 1939 UNITED STATES PATENT OFFICEv Ralph R. Chappell, Richmond, Va., and Kenneth E. Whitney, Baltimore, Md., asslgnors to Bendix Aviation Corporation,

South Bend,

Ind., a corporation of Delaware Application June 26, 1936, Serial No. 87,568

12 Claims.

This invention relates to instruments and more particularly to instruments for determining atmospheric conditions, such as temperature and humidity.

One of the objects of the present invention is to provide novel means in combination with a psychrometer whereby the degree of moisture of theatmosphere may be quickly and accurately measured in any desired location.

It has been heretofore proposed to provide portable psychrometers which are rotatably mounted so that the same may be manually swung through the air in a particular location and thus quickly and readily obtain an indication from which the degree of aqueous vapor of the atmosphere may be determined. In order to obtain accurate readings with an instrument of this character, the operator must possess a certain amount of skill in the handling of the same and even in the hands of a skilled operator the centrifugal forces acting upon the mercury or similar fiuid in the thermometers creates some inaccuracy in the indication. Furthermore, the use of a sling psychrometenas the above type is commonly designated, creates a disturbance and distraction, thereby making the use of the same somewhat undesirable in theaters, oices, etc. and there is the additional danger of flinging moisture from the wet to the dry bulb during operation. There is also the disadvantage that the moisture in the wick of the wet bulb is caused by centrifugal forces to concentrate at the outer or lower end of said wick.

It is accordingly another object of the invention to provide a novel psychrometer wherein the accuracy of the readings is not affected by the skill or lack of skill of the operator.

Still another object is to provide novel means in combination with a psychrometer whereby a reading may be obtained at any place without creating a disturbance or attracting the attention of other persons in the vicinity.

A further object is to provide a novel portable psychrometer, wherein the thermometers are maintained in a readable position at all times during use.

A still further object is to provide a portable psychrometer which is small and compact, yet simple in construction and operation and extremely accurate.

Another object is to provide a novel means and method for quickly determining the temperature in a particular location.

The above and further objects and novel features oi the invention will more fully appear from the following detailed description when taken in connection with the accompanying drawing. It is to be expressly understood, however, that the drawing is for the purpose of illustration only and is not designed as a definition of the limits 5 of the invention, reference being primarily had for this latter purpose to the appended claims.

In the drawing, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is an isometric plan view, with parts broken away, of one form of instrument embodying the present invention, the casing being shown in open position;

Fig. 2 is a detail top plan, on an enlarged scale 15 and with parts broken away, of the device of Fig- Fig. 3 is a sectional side elevation, partly in section and with parts broken away, the section being taken substantially on line 3-3 of Fig. 2; 20 and Fig. 4 is a sectional end view taken on line 4-4 of Fig. 2.

In the form in which the invention is illustrated in the drawing, by way of example, a psy- 25 chrometer is housed in a small, two-piece casing comprising a flat or plane base IU and a flanged cover member II. Said cover and base are pivotally secured together at one end thereof by means of pins I2, and the former may be em- 30 ployed as a handle for supporting the entire assembly when the casing is opened. Cover II' may be yieldingly held in closed position by a resilient tongue portion of a bracket I3 which is secured to base I0 by means of a small screw, 35 said tongue being adapted to engage a head II on the flange of said cover.

A pair of thermometers I4 and I5 of any suitable type, the former a dry bulb and the latter a wet bulb thermometer, are preferably secured 40 to and laterally spaced from one another on base I0 by means of bracket I3. The lower ends or bulbs I6 and I1 of thermometers I4 and I5, respectively, extend into and are enclosed by a small housing I8 which is secured to plate I0 by means 45 of screws I8 that extend through a pair of brackets formed integrally with said housing. Bulbs I6 and I1 are filled with mercury, or other suitable substance, and bulb Il is covered with a mesh wick I9 which is dampened with distilled 50 water. Casing I8 is preferably highly polished to provide effective thermo shielding for the thermometer bulbs to thereby increase the accuracy of the readings.

A pair of elongated air inlet openings 20 are 55 provided in opposed sides of the central or body portion of housing I8, whereby air from the surrounding atmosphere may be drawn into thev housing, in a novel manner to appear hereafter, and be caused to pass around bulbs I6 and I1 in contact therewith. In order to insure that the air entering openings 20 will pass in close proximity to the bulbs, the top and bottom of said body portion of housing I8 is formed with a Wavelike contour to thereby form three somewhat cylindrical, intercommunicating compartments a, b and c, as best seen in Fig. 4. Since the bulbs of the thermometers are centrally disposed in compartments a andb, air currents which are induced to enter openings 20 and iiow into center compartment c must pass substantially completely around bulbs I6 and I1 and flow closely adjacent the same. The central portion of housing I8 is preferably made in two similarly shaped parts, the lower of which, as viewed in the drawing, is rigidly secured to the end walls of the housing, whereas the upper part, in the form shown, overlaps the lower part and is removably held in position by its own resiliency. Said upper part may thus be readily removed when it is desired to apply moisture to wick I 8. If desired, however, said upper part or cover of housing I8 may be hingedly secured in position so that said part need not be entirely removed to permit access to the interior of the housing.

Novel means are also provided whereby an articial flow of air over bulbs I6 and I1 may be created for the purpose of causing thermometers I4 and I5v to quickly respond to changes in temperature, such as when the same are moved from one location to another, and to give a true and accurate indication of the wet and dry bulb temperatures in any chosen locality, from which temperatures the humidity may be readily determined. In the form shown, said means comprises.

a Venturi tube 2|, the suction or low pressure end of which extends into an outlet opening in the end wall of housing I6 and communicates with the central compartment c of the latter. Extending through the opposite end wall of housing I8, through said central compartment, and into tube 2I is a conduit 22. The latter terminates adjacent throat 23 of Venturi' tube 2| and is provided with a restricted passage or nozzle 24 at the end thereof. Thus, when a gaseous medium, such as air, is forced through conduit 22 under pressure, a jet of air is projected from nozzle 24 through throat 23 at a high velocity, said jet of air Ahaving an ejector effect and being adapted to entrain air from the annular chamber 25 around conduit 22, thereby creating subatmospheric pressure in said chamber and in compartment c. Large quantities of air rush into this low pressure area from the surrounding atmosphere through openings 28 and over bulbs I6 and I1.

Novel manually operable means are provided for supplying the high speed jet of air to Venturi throat 23, wherebt7 a smooth, steady ow of air is induced over bulbs I6 and I1, said means in the illustrated embodiment being constituted by pump means in the form of a flexible bulb 26 having a one-way valve 21 of any suitable type in the inlet opening thereof, and a ilexible pressure reservoir 28 which is connected to the outlet of pump 26 through a one-way valve (not shown) which permits flow from the pump to the reservoir, the latter constituting means for smoothing out the pressure impulses of pump 26, whereby a steady, even supply of air through nozzle 24 is provided.

Reservoir 26 communicates with conduit 22 through a flexible hose 29 which may be integral with said reservoir, a'nipple 30 which' extends through the wall oi' casing cover I I and to which one end of hose 28 is removably connected, and 5 When it is desired to obtain a reading in a 10 particular location in a. theater, for example, or in a room in which thermometers are not installed, the above described instrument is carried to that location, the casing opened, as seen in Fig. 1, and a pressure built up in reservoir 28 15 by manually pulsating pump 26. Air under pressure thus ows from the reservoir through hose 29, nipple 30, conduits 8|, 22 and nozzle, creating a jet oi.' air which moves at a high velocity through throat 23 of Venturi tube 2|. This rapidly moving jet of air is eiective to entrain the surrounding or ambient air and thereby lower the pressure in annular chamber 25 and hence in housing I 8. Air which is representative of the true atmospheric conditions prevailing in the locality in which the reading is being taken is accordingly drawn into housing I8 through inlet openings 20, directed over bulbs I6 and I1 in proximity thereto by the contqur oi' the walls of said housing. and discharged through the outlet 3 passage to which Venturi tube 2I is connected. 'I'he ow of air over bulbs I6 and I1 will be steady and uniform since the pulsations of pump 26 are. y

smoothed out by reason of the resiliency oi' reservoir 28, and the flow over each of said bulbs will be substantially equal. It will be noted that air from pump 26 doesy not come into contact with bulbs I6 and I1, thereby obviating any error which might otherwise be caused by the temperature changes of the air resulting from friction, compression and expansion. Neither does the air which contacts the wet bulb Wick I9 and becomes partially saturated with moisture contact dry bulb I6 and thereby create an error in the reading of thermometer Il. A correct and accurate indication of both the wet and dry bulb temperatures may thus be obtained in a very short space of time. The humidity in that location may then be determined from suitable tables or charts or by the use of a psychrometric slide rule or the like.

There is thus provided a novel portable instrument whereby the temperatures as registered by` wet and dry bulb thermometers may be readily, quickly and accurately obtained in any locality without subjecting the instrument to the action of centrifugal forces, the accuracy of the indications of the thermometers being independent of the skill of the operator. The grave'chances of error that exist in portable psychrometers heretofore provided are substantially eliminated in a device embodying the present invention. 'I'he instrument provided is easy to operate and may be used in crowded locations without attracting the attention of bystanders.

Although only one embodiment of the present invention has been illustrated and described in detail, it is to be expressly understood that the same is not limited thereto but that various changes may be made therein, such as in the design and arrangement of the parts illustrated, without departing from the spirit and scope of the invention, as will now be apparent to those skilled in the art; For a definition of the limits 75 of the invention, reference will be had primarily to the appended claims.

What is claimed is:

l. In a weather instrument, the combination of a thermometer, a compressible bulb, means including a Venturi tube connected to said bulb for producing a suction and inducing a flow of air by said suction, means conducting said air over the bulb of said thermometer, and portable means for mounting said thermometer, said conducting means and said venturi.

2. In a weather instrument, the combination of a Wet bulb thermometer, a dry bulb thermometer, a Venturi tube having one end thereof adjacent the bulbs of said thermometers, and manually operable means for directing a jet of air under pressure through said Venturi tube at a high velocity to create a suction at the end of said tube between said bulbs whereby said suction produces a iiow of air over the bulbs of said thermometers.

3. In a weather instrument, the combination of a wet bulb thermometer, a dry bulb thermometer, a perforated housing surrounding the bulbs of said thermometers, means for creating super-atmospheric pressure to cause a flow of air, and means for creating by said ow of air a sub-atmospheric pressure in said housing whereby a ow of other air is induced and means for directing said ow in two separate paths over said wet and dry bulbs.

4. In a weather instrument, the combination of a Wet bulb thermometer, a dry bulb thermometer, a perforated housing surrounding the bulbs of said thermometers, and means for creating a sub-atmospheric pressure in said housing whereby a flow of air over said bulbs is induced, said means including a Venturi tube in communication with said housing and manually operable pump means for forcing air through the throat of said Venturi tube to create a sub-atmospheric pressure in said housing.

5. In a weather instrument, the combination of a Wet bulb thermometer, a dry thermometer, a housing enclosing the bulbs of said thermometers, said housing having inlet and discharge openings therein, a Venturi tube connected to said discharge opening, and manually operable means for forcing air through said Venturi tube at a high velocity to create a now of air through said inlet openings and over said bulbs.

6. In a weather instrument, the combination of a wet bulb thermometer, a dry bulb thermometer, a housing enclosing the bulbs of said thermometers, said housing having inlet and discharge openings therein, and means for creating a now of air over the bulbs of said thermometers, said means including a Venturi tube connected to said discharge opening, a nozzle within said tube adjacent the throat thereof and manually operable air compressing means connected to said nozzle.

7. In a weather instrument, the combination of a Wet bulb thermometer, a dry bulb thermometer, a housing surrounding the bulbs of said thermometers having a separate chamber for each bulb, inlet openings in said respective chambers, a centrally disposed outlet opening, and means for creating a sub-atmospheric pressure at said outlet opening to cause separate iiows of air over the bulbs of said thermometers.

8. In an instrument of the class described, a two part casing, means for pivotally securing the two parts of said casing together, a pair of thermometers rigidly mounted adjacent each other on one of said parts, a housing enclosing the bulbs of said thermometers, said housing having an opening adjacent each of said bulbs, a Venturi tube communicating with said housing, a conduit extending into said tube and terminating adjacent the throat thereof, a restricted passage in said conduit, and means for l supplying air under pressure to the latter.

9. In apparatus of the class described, a wet bulb thermometer, a dry bulb thermometer, means for creating a flow of air over the bulbs of said thermometers, said means including a Venturi tube, a conduit extending into said tube and terminating adjacent the throat thereof, a

restricted passage in said conduit and means for supplying air under pressure to said conduit, said last named means comprising a pressure reservoir, manually operable means for building up air pressure in said reservoir and means providing a path from said bulbs to said venturi.

10. In a weather instrument, the combination of a Wet bulb thermometer, a dry bulb thermometer, and means for creating a flow of air over the bulbs of said thermometers, said means including a Venturi tube, a nozzle within said tube adjacent the throat thereof, a source of compressed air, means connecting said source and said nozzle and means providing a path from said bulbs to said venturi.

11. A portable psychrometer, comprising a wet bulb thermometer, a dry bulb thermometer, and means for delivering fluid flow to said members, said means including manually compressible volume reducing means for providing a flow of air, and means for directing said flow in two separate parts, one part passing over one thermometer only.

12. In a weather instrument, the combination of a thermometer, a compressible bulb, means including a Venturi tube connected to said bulb for producing a suction and inducing a flow of air by said suction, means conducting said air over the bulb of said thermometer, a portable casing, and a cover for said casing, said thermometer said conducting means and said venturi being mounted on said cover.

RALPH R. CHAPPELL. KENNETH E. WHITNEY. 

